Electric utility companies charge users on a three pronged basis. First, the demand rate is determined; that is, the greatest demand for electricity required by the user over a specific period of time, typically a fifteen(15) minute period, is determined. For example, if several electrical devices in the form of appliances or other loads come on line simultaneously and all draw power over the fifteen(15) minute period, the demand is high and electrical utility companies charge in accordance with the highest demand incurred that entire month or year depending on the utility. If the demand rate is smaller, the rates are lower and concomitantly, the electricity cost is lower for the same amount of energy consumed but which is consumed over a longer time period. Second, the total consumption of electricity is determined by the electric utility. If total consumption of electricity is smaller, electric utility costs will be lower as is well known. Third, the power factor of loads which utilise motors, such as refrigerators, freezers, heating, air conditioning and ventilating ("HVAC") equipment and the like is of interest as is the type of meter used to measure such inductive loads. Utility companies take the view that most motors have a power factor of about 0.64 which is not unreasonable if there is no attempt to increase the power factor and if the user is a relatively small user of electrical power. The power measured at the meter is the power rating of the motor divided by the power factor. If the power factor is close to unity, the lower the power measured at the meter and the lower the cost of power. If the user can show that its power factor is between 0.9 and 1.0, electric utility companies will generally negotiate a lower rate for supplied electricity thereby resulting in lower costs. A particular disadvantage to the utility customer results if the meter measuring the reactive power associated with motors is a thermal type meter.
In restaurants, gas stations and convenience and grocery stores, electrical power consumption is relatively high and the three factors described above for use in determining electric power costs are particularly disadvantageous for the user. This is so because, first, it is often the case that several loads, appliances or other devices commence operation and draw power simultaneously such as will happen, for example, when the manager of such a business commences the operation of several loads and other devices when the establishment is initially opened in the morning. Such activities include switching on coffee makers, toasters, heating, ventilating or air conditioning units ("HVAC") and food heaters simultaneously. Thus, the demand rate is very high at this particular period and this high demand rate which will extend generally for at least the fifteen(15) minute demand period which then sets the rates charged by the electrical company to the customer for electric power over an entire month or year of consumption. It may and usually is unnecessary to have this high demand. Thus, the simultaneous operation of many different loads, particularly at their full power settings, is disadvantageous.
Secondly, motors under operation contain high inductance and the use of motors can result in low power factors. For example, a restaurant may contain several walk-in freezers/coolers or refrigerators/coolers used to freeze or display food items for customers and to maintain food for preparation. HVAC equipment likewise contains motors for compressors and fans. The use of such motors for running compressors or otherwise causes the voltage to lag the current by an amount that is quantified as the power factor. A low power factor is disadvantageous for the user who pays unnecessarily high electricity rates for using such motors. This disadvantage is particulary pronounced when the reactive power is measured by a thermal type meter.
Thirdly, restaurants are inefficient users of electricity. Continuously operating toasters, coffee machines, pizza ovens, food warmers and the like draw high power when no toast or food is being prepared. Such high power use is unnecessary, disadvantageous and costly.
An energy management system is disclosed in U.S. Pat. No. 5,572,438 (Ehlers et al) and assigned to TECO Energy Management Services. This reference is primarily oriented towards energy conservation and control information being provided to the user and not to automatic energy consumption reduction by a plurality of loads at the location of the consumer. Ehlers et al teach a communication technology preferably using power-line carrier (PLC) technology between a control computer located at the facility and a utility meter at the user's location. Such technology is not a principal concern of the applicant since control of energy consumption by the utility supplying such energy is not a material aspect of the present invention.